//********************************************************************************************************
// Product Name: MapWindow.dll Alpha
// Description:  The basic module for MapWindow version 6.0
//********************************************************************************************************
// The contents of this file are subject to the Mozilla Public License Version 1.1 (the "License"); 
// you may not use this file except in compliance with the License. You may obtain a copy of the License at 
// http://www.mozilla.org/MPL/ 
//
// Software distributed under the License is distributed on an "AS IS" basis, WITHOUT WARRANTY OF 
// ANY KIND, either expressed or implied. See the License for the specificlanguage governing rights and 
// limitations under the License. 
//
// The Original Code is from MapWindow.dll version 6.0
//
// The Initial Developer of this Original Code is Ted Dunsford. Created 2/18/2010 3:12:48 PM
// 
// Contributor(s): (Open source contributors should list themselves and their modifications here). 
//
//********************************************************************************************************

using System;
using System.Collections;


namespace MapWindow.Data
{


    /// <summary>
    /// CRC32
    /// </summary>
    public static class Crc32
    {
        private static UInt32[] _createdTable;

        private static readonly UInt32[] CRCTable =
        {
            0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
            0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
            0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
            0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
            0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
            0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
            0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
            0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
            0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
            0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
            0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
            0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
            0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
            0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
            0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
            0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
            0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
            0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
            0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
            0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
            0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
            0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
            0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
            0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
            0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
            0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
            0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
            0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
            0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
            0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
            0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
            0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
            0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
            0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
            0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
            0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
            0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
            0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
            0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
            0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
            0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
            0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
            0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
            0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
            0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
            0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
            0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
            0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
            0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
            0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
            0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
            0x2d02ef8d
        };
         
        /// <summary>
        /// Calculates the CRC-32-IEEE 802.3 Checkzum for png according to:
        /// x^32 + x^26 + x^23 + x^22 + x^16 + + x^12 + x^11 + x^10 + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1 
        /// </summary>
        /// <param name="value"></param>
        /// <returns></returns>
        public static byte[] GetCrcOld(byte[] value)
        {
           
            UInt32 crcVal = 0xffffffff;
            for (int i = 0; i < value.Length; i++)
            {
                crcVal = (crcVal >> 8) ^ CRCTable[(crcVal & 0xff) ^ value[i]];
            }
            crcVal ^= 0xffffffff; // Toggle operation
            byte[] result = new byte[4];
            result[0] = (byte)(crcVal >> 24);
            result[1] = (byte)(crcVal >> 16);
            result[2] = (byte)(crcVal >> 8);
            result[3] = (byte)(crcVal);
            return result;
        }

        static uint[] table;

        public static uint ComputeChecksum(byte[] bytes) 
        {
            if(table == null) table = CreateTable2();
            uint crc = 0xffffffff;
            for(int i = 0; i < bytes.Length; ++i) 
            {
                byte index = (byte)(((crc) & 0xff) ^ bytes[i]);
                crc = (uint)((crc >> 8) ^ table[index]);
            }
            return ~crc;
        }

        public static byte[] ComputeChecksumBytes(byte[] bytes) 
        {
            return BitConverter.GetBytes(ComputeChecksum(bytes));
        }

        public static uint[] CreateTable2()
        {
            uint poly = 0xedb88320;
            table = new uint[256];
            uint temp = 0;
            for (uint i = 0; i < table.Length; ++i)
            {
                temp = i;
                for (int j = 8; j > 0; --j)
                {
                    if ((temp & 1) == 1)
                    {
                        temp = (uint) ((temp >> 1) ^ poly);
                    }
                    else
                    {
                        temp >>= 1;
                    }
                }
                table[i] = temp;
            }
            return table;
        }


        /// <summary>
        /// Calculates the CRC-32-IEEE 802.3 Checkzum for png according to:
        /// x^32 + x^26 + x^23 + x^22 + x^16 + + x^12 + x^11 + x^10 + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1 
        /// </summary>
        /// <param name="value"></param>
        /// <returns></returns>
        public static uint GetCrc2(byte[] value)
        {
            uint val = UpdateCrc(0xffffffff, value, value.Length) ^ 0xffffffff;
            byte[] vals = BitConverter.GetBytes(val);
            for (int i = 0; i < 4; i++)
            {
                vals[i] = (byte)~vals[i];
            }
            return BitConverter.ToUInt32(vals,0);
            //return Reverse(val);
        }

        static uint Reverse(uint val)
        {
            byte[] vals = BitConverter.GetBytes(val);
            // first reverse the byte order
            Array.Reverse(vals);
            // then reverse the bit order of each byte
            for(int i = 0; i < 4; i++)
            {
                vals[i] = ReverseByte(vals[i]);
            }
            return BitConverter.ToUInt32(vals, 0);
        }

        static byte ReverseByte(byte b)
        {
            byte r = 0;
            for (int i = 0; i < 8; i++)
            {
                int mask = 1 << i;
                int bit = (b & mask) >> i;
                int reversedMask = bit << (7 - i);
                r |= (byte)reversedMask;
            }
            return r;
        }


        /// <summary>
        /// Updates the running CRC
        /// </summary>
        /// <param name="crc"></param>
        /// <param name="buff"></param>
        /// <param name="len"></param>
        /// <returns></returns>
        public static UInt32 UpdateCrc(UInt32 crc, byte[] buff, int len)
        {
            UInt32 c = crc;
            int n;
            if (_createdTable == null) _createdTable = CreateTable();
            for(n =0;n<len;n++)
            {
                c = _createdTable[(c ^ buff[n]) & 0xff] ^ (c >> 8);
            }
            return c;
        }


        /// <summary>
        /// Creates the table according to the png specification
        /// </summary>
        /// <returns></returns>
        public static UInt32[] CreateTable()
        {
            _createdTable = new uint[256];
            for (int n = 0; n < 256; n++)
            {
                uint c = (uint) n;
                int k;
                for(k = 0; k < 8; k++)
                {
                    if ((c & 1) > 0)
                    {
                        c = 0xedb88320 ^ (c >> 1);
                    }
                    else
                    {
                        c = c >> 1;   
                    }
                }
                _createdTable[n] = c;
            }
            return _createdTable;
        }


    



    }
}
